1. Field of the Invention
The present invention is related to the medical field, in particular in operative methodology during the preparation and carrying out of surgical interventions.
The invention relates in particular to medical imaging and, in the perioperative phase, to the automated acquisition of anatomical surfaces, in particular of a patient's head and face, then the surface resetting of the acquired images with respect to images stored in pre-operative phase.
The invention will find an application in the assistance by robotics for the acquisition of anatomical surfaces and for the surface resetting.
To this end, the present invention relates to a method for automated and assisted acquisition of anatomical surfaces.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
In a known way, during a surgical operation on a patient, in particular within the framework of the neurosurgery at the level of a patient's head, the doctor uses systems providing an assistance, in particular by improving the surgical accuracy. To this end, such systems permit, in the perioperative phase, the acquisition of the anatomical surfaces aimed by the operation, then their resetting with respect to images already recorded, for example previously, during a pre-operative phase during an X-ray examination (CT-scan) or an MRI (stands for Magnetic Resonance Imaging). It is thus possible for the doctor to accurately localize the patient with respect to the imaging for the operation.
In particular, the acquisition consists in identifying the actual position of the patient's anatomical zone, by performing a scanning of the surface of said zone using a pointer, for example in the form of a mechanical point, ultrasonic waves or a laser beam. The system then performs a surface resetting in the form of a comparison between this identification and the images recorded previously in the pre-operative phase, calculating the bringing into correspondence of the existing images with the patient's body at the time of the operation. In brief, for each identified point, an evaluation is performed so as to cause the acquired scatter diagram to correspond to the pre-recorded images.
Therefore, the way of performing the step of acquisition of the anatomical surfaces has a considerable influence on the accuracy of the operation that will follow. Several acquisition systems exist nowadays, which use different techniques for identifying the anatomical surfaces.
A first solution consists in positioning, at different particular places of the zone to be acquired, markers, in the form of a mask or pads, directly glued on the skin. These markers are then identified in the space by scanning with a mechanical point or a transmission/receiving beam, namely a laser.
The main drawback of such a scanning resides in its lack of accuracy, which depends on the way of localizing said markers as well as their number and their spatial distribution on the skin. The resetting resulting from the same is then little reliable, i.e. it exhibits important variations and shifts at the level of the surfaces located between the markers.
In addition, the markers can move, because of the elasticity of the skin, even detach. The placing of the markers also obliges to shave the portion of the cranium.
An alternative solution consists in passing over the anatomical zone with a pointer, the coordinates of which are located in the space, in particular through cameras.
According to an embodiment, said pointer can be mechanical, being in the form of a probe, the point of which enters directly into contact with the skin. Said point is manually displaced from one point to another, namely on the morphologically noteworthy points, and along particular anatomical lines of the zone involved, while its different positions and contact points are recorded in three dimensions.
However, though this technique permits to identify a larger number of points of the surface, it remains limited as to the number of points identified, about one hundred, requiring a restriction of the identification to determined lines and determined noteworthy places of the patient's anatomy. This restriction, due to the intervention by the operator, has automatically an influence on the quality of the subsequent surface resetting. Furthermore, the deformation of the skin during the scanning with the pointer is another cause for inaccuracy.
An alternative resides in a contactless pointer, permitting to obtain a larger number of points identified in a smaller period of time. Such a pointer is in the form of a light-radiation transmitter, such as a laser beam. Said transmitter is held in hand by the practitioner, who scans the anatomical zone with the laser.
A first known device comprises a transmitter in the form of a laser telemeter, the position and the orientation of which are constantly identified in the space, permitting to obtain the coordinates of each point recorded by the telemeter.
However, the accuracy of the identification by the telemeter remains limited. That is why it has been devised to directly record the impact of the emitted laser beam at the level of the skin. To this end, the transmitter transmits, on the one hand, a laser beam in the visible light spectrum, in order to allow the practitioner to display the point of impact and its scanning of the patient's anatomical zone and, on the other hand, a beam of invisible light, such as the infrareds, which are captured by specific sensors. Specifically, the reflection of the infrareds at the point of impact permits to accurately identify the position of said point in the space.
It should be noted that the localization of the telemeter or the point of impact of the laser beam uses an optical triangulation principle using various cameras.
Despite these various evolutions, the existing identification and scanning systems are not completely satisfactory.
Indeed, the scanning always occurs manually, creating a human factor, which reduces the accuracy of the identification, but also its repeatable nature, i.e. the scanning paths remain approximate and completely related to the practitioner.
In order to cope with these drawbacks, it has been devised to couple the transmitter to a robot. Such solutions are described in WO 2009/013406, WO 2005/122916 and WO 2005/032390.
In particular, the transmitter is fixed to the end of a robotized arm, hinged so as to have degrees of freedom of movement in the three dimensions. The position of the transmitter and the data it records are then identified in the space with respect to the reference system of said robotized arm.
In particular, a first previous acquisition of said anatomical surfaces is performed, so as to create a three-dimensional representation in the form of a first digital model; then, a second perioperative acquisition by scanning said surfaces is performed, so as to create a three-dimensional representation in the form of a second digital model; then, said scanning is performed with means for identifying the coordinates of said surfaces, said means being supported by a robotized arm; and finally a bringing into correspondence by resetting said first and second models is performed.
Therefore, one observes that the resetting of the models is not optimal, requiring the intervention of a data-processing operator, in order to try to cause the models to match. When this fails, it is necessary to repeat the scanning operation, increasing that more the duration of the intervention.
In addition, even though such devices permit to avoid depending from the operator, by automating the scanning of the anatomical surface, with a highly reproducible nature, this automation considerably limits the capabilities of adaptation of these devices with respect to the anatomical zone, in particular with respect to the different morphologies of the patients.
Furthermore, in all cases the existing devices use means for navigating within the display of the three-dimensional digital model obtained from the images so acquired. These navigation means necessarily require the identification of the transmitter, as previously evoked, thereafter of the surgical instruments.